Hoya Corporation

Hoya Glass Disk (thailand) Ltd.

Yoshinori Marumo

Takashi Maeda

Hideki Isono

Toshio Takizawa

Shinji Eda

Hiroshi Tsuchiya

Masahiro Katagiri

Takumi Koshimizu

Intanon Sitalaphruek

Provided are a magnetic disk substrate and a method of manufacturing the same, wherein the magnetic disk substrate has very few defects present on its surface with an arithmetic mean roughness (Ra) at a level in the vicinity of 0.1 nm and thus is suitable as a substrate for a magnetic disk with high recording density. The magnetic disk glass substrate is such that the arithmetic mean roughness (Ra) of the main surface of the glass substrate measured using an atomic force microscope with a resolution of 256&#xd7;256 pixels in a 2 &#x3bc;m&#xd7;2 &#x3bc;m square is 0.12 nm or less and the number of defects detected to have a size of 0.1 &#x3bc;m to 0.6 &#x3bc;m in plan view and a depth of 0.5 nm to 2 nm is less than 10 per 24 cm, wherein the defects are each detected using a shift in wavelength between incident light and reflected light upon irradiating and scanning helium neon laser light with a wavelength of 632 nm on the main surface of the glass substrate.

Glass substrate for a magnetic disk and magnetic disk

When mirror polishing is performed on a glass substrate by bringing a polishing pad into contact with the surface of the glass substrate while supplying a polishing liquid containing polishing grains to the substrate surface, the pH of the polishing liquid is maintained within a certain range or the agglomeration degree or dispersion degree of the polishing liquid is controlled. Consequently, an adequate mirror polishing rate can be maintained and there can be obtained a glass substrate having a good end shape.

Method for producing glass substrate for magnetic disk and method for manufacturing magnetic disk

In a manufacturing method of a glass substrate for a magnetic disk including a cleaning process of the glass substrate, the cleaning process includes a process of contacting the glass substrate with a cleaning solution containing a compound, such as thioglycolic acid or a thioglycolic acid derivative, having a thiol group as a functional group.

Method of manufacturing a glass substrate for magnetic disk

Method of manufacturing glass substrate for magnetic disk

A method for manufacturing a glass substrate for a magnetic disk comprises mirror surface polishing and cleaning of a glass substrate, wherein polishing agent of which the principal component is rare-earth oxide with content of fluorine 5% by weight or less, is supplied to the glass substrate, the surface of the glass substrate is subjected to mirror surface polishing by relatively moving the polishing cloth and the glass substrate, then this glass substrate is brought into contact with a cleaning solution including ascorbic acid, fluorine ion, and sulfuric acid of 3% by weight or more, and the polishing agent is dissolved and removed. The concentration of the ascorbic acid included in the cleaning solution is 0.1% by weight or more, and the content of the fluorine ion is 1 ppm to 40 ppm. At least a magnetic layer is formed on the obtained glass substrate to manufacture a magnetic disk.

Manufacturing method of glass substrate for magnetic disk, and manufacturing method of magnetic disk

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Tokyo, Japan

Yoshinori Marumo